The invention relates to a hydraulic rock breaking device provided with a percussion device. With the percussion device, impact pulses can be given to a tool connected to the rock breaking device, the tool further transmitting the impact pulses to the material to be broken. Further, the invention relates to a protection valve arrangeable in the inlet channel of a hydraulic percussion device being part of a rock breaking device. Further still, the invention relates to a method of operating such a rock breaking device.
The objects of the invention are defined in greater detail in the preambles of the independent claims of the application.
A breaking hammer is used as an auxiliary device of an excavator or another work machine when the intention is to break for instance rock, concrete or other relatively hard material. The breaking hammer comprises an percussion device with which impacts can be given to a tool attached to the breaking hammer, the tool further transmitting the impacts to the material to be broken. The percussion device is usually hydraulic and comprises a percussion piston having, due to the effect of hydraulic pressure, reciprocal movement and striking the impact surface at the upper end of the tool. At the same time as impacts are given with the percussion piston, the tool is pressed against the material to be broken, whereby the tool penetrates into the material to be broken due to the effect of the impact and the pressing, causing breaking of the material.
Hydraulic breaking hammers are typically connected to a work machine as an auxiliary device. Modern excavators have a computer-controlled control unit which allows the volume flow and the operating pressure fed to each auxiliary device connected to the excavator to be controlled. The operator can easily select the correct settings for each auxiliary device by means of the control unit. It is possible, however, that the operator erroneously selects the incorrect settings for the breaking hammer, in which case the breaking hammer may be operated in such a way that too large a volume flow or too high a pressure have been fed in, i.e. with an excessively high input power. Feeding too high a power to the breaking hammer may cause the hammer to break or wear out prematurely. Feeding incorrect power to the breaking hammer may be a mistake but it has also been observed that some operators select incorrect settings for the breaking hammer in purpose with the intention of improving the output power of the breaking hammer by means of the excessively high input power. In such a case, however, the improvement in the power is achieved at the cost of the durability of the device, which is naturally not acceptable. Thus, the problem is that for some reason or other, an excessively high input power can be fed to the breaking device.